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Post subject: Re: DRRI Bias - from Stock GT to EH
Posted: Wed Jul 06, 2011 6:11 am
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Read and understand BMW's frustration on the new Tung-Sol 6V6s.
viewtopic.php?f=12&t=56864


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Post subject: Re: DRRI Bias - from Stock GT to EH
Posted: Wed Jul 06, 2011 6:16 am
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+1 rebelsoul

And new made Tung Sol is now only a name..... nothing to do with the real thing.

How we call that ? Vintage hip ?


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Post subject: Re: DRRI Bias - from Stock GT to EH
Posted: Wed Jul 06, 2011 7:21 am
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If anyone can get good tone and fairly good life outta these new "reissued" TungSol 6V6GT, maybe it's in a Deluxe Reverb. One running over 425-450 VDC onto the plates. And therefore can drop the idle bias down into the the 20-25mA range. New Sensor guarantees, whatever that really means, the TSRI can handle 450 VDC for hours, at a time. According to Mike Matthew's testing.

One thing for sure---they do not like constant high idle bias.

I've tried the tubes in several (like 4 different era Princetons) and two Champs (one BF and one SF). They do not like the lower plate volts of the PR (around 415-420 VDC). As I need to really crank the idle bias current up above 25mA (some close to 30mA) to get any good tone outta the amp.

And the Class "A" setting of the Champs demands that the tube stays (more-or-less) "on" all the time. So for the first 15 minutes, things are ok. But, after 30 minutes of diming the thing, the tube really starts to overheat and show red spots on the plates.

I'm restoring a 1965 BF VC right now. Going to need to put in new iron. Got it with fried and oozing OPT, PT, and popped cap can. Excellent exterior, so I think old owner had a runaway power tube, that he didn't notice, before frying the OPT and PS circuit. I've seen these in old Champs & Princetons with two-wired AC cords that often had 2A fuses (seem like OEM Littlebuss). One actually had the bottom of the can pop off and splatter it's guts all over the chassis. A mess. But, with some elbow grease and a good 1amp Slow-Blow, new NOS Sprague can (I keep these in cold storage), the amp has been very reliable ever since (I got it back in 1995, for $25).

If you wire the thing for three-prong AC wiring. Put the black (hot) to the fuse. Use a good (not Chinese made) 1amp Slow-Blow fuse. The amp seems to be much more stable and not as sensitive to the outlet you plug the amp into. Something, I've been hashing about on another amp board.

Right now, going to try the TAD 6V6GT and selected JJ 6V6S (though not a big fan of its tone). The amps I use regularly have NOS US made 1950-60's tube, Brimar 6V6GTY, or Visseaux or Mazda French 6V6GT. Those tubes are "bias, turn on, and forget" tubes. Very reliable with consistent tone.

And now collecting as many NOS 6V6G (coke bottle) VT-117A or VT-117B--- as most ppl don't realize they run at same specs as the 6V6GT. So, you can still get them at fairly good price. And try hunting for Brimar 6V6GTY. They are hardy tubes made to US military standards of the 1950's.


Last edited by BMW2002Ti on Wed Jul 06, 2011 7:25 am, edited 1 time in total.

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Post subject: Re: DRRI Bias - from Stock GT to EH
Posted: Wed Jul 06, 2011 7:24 am
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shimmilou wrote:
That's odd. :? The spec sheet for a GE 6V6 GT says 14 watts, Tungsol 6V6 GT 14 watts, among others as I mentioned before, and both the RCA GT and GTA are 14 watts. So why would they say only 12 watts for a 6V6 GT?

The Weber calculator site is worthless to me, I can already multiply two numbers. And, if you notice, the Weber calculator keeps changing the entered number for the Cathode current, dropping 2 mA from any number entered. Is this their way of subtracting the screen currents? The screen current(s) are closer to 5 mA than 2 mA for a 6L6. :?:

Again, is there a spec sheet that shows only 12 watts for a 6V6? Some sheets show 12 watts or 14 watts depending on the configuration, for the same tube, which means max 14 watts. :idea:

But, I agree with erring on the conservative side if unsure. :idea:


For someone who understands bias, the Weber site is not necessary. For those many who don't have a clue, I think it is very valuable as a teaching tool.

No, the bias calculator does not always subract "2" from the cathode current to get plate current (Try different values, I did.), it subtracts 5% (This is all stated on the site. They are not hiding anything.). It does round off, though, but for all practical purposes is close enough, since I think we can all agree that proper bias is a range of values and not a specific number.

I have no answer for the question regading 12 or 14 watts for a 6V6, but like Shillilou, the spec sheets I have seen show 14 watts (which is "about 15 watts" :lol: ). I stick with 6L6GCs. :D

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Post subject: Re: DRRI Bias - from Stock GT to EH
Posted: Wed Jul 06, 2011 7:27 am
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stratele52 wrote:
I understand all of that. It is made quite clear in the Weber bias tables. It is this statement that I do not understand:

"adjust bias many times until no plate voltage change and you have correct bias."
_Bluesky

Yes you are right Bill

Louis


Ummm, I have no idea what you are saying I am right about. The statement in quotes is yours and makes no sense to me.

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Post subject: Re: DRRI Bias - from Stock GT to EH
Posted: Wed Jul 06, 2011 7:30 am
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cedarblues wrote:
I just looked up the spec sheet on the TAD I've been running in my DRRI, bias is at 20 mA right now... not sure what it all means but it looks like 15 W.

http://www.tubeampdoctor.com/images/File/TAD-Datenblatt_6V6GT-STR%20Version1.0-05.07.11.pdf

Until someone convinces me that it's safe to run my tubes hotter I'll stick with these safe #s :wink:


You're just running your tubes a little colder than they probably need to be. If you are happy with the tone, that's the only thing that matters, not the number. :D

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Post subject: Re: DRRI Bias - from Stock GT to EH
Posted: Wed Jul 06, 2011 9:15 am
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bluesky636 wrote:
You're just running your tubes a little colder than they probably need to be. If you are happy with the tone, that's the only thing that matters, not the number. :D

If the TADs are also 14 Watts then at 20 mA they're at 60%. Plate voltage is right at 420 with 20 mA in my DRRI. I can bias 'em at 23 mA and see how they behave... but yeah, they do sound sweet at 20, very similar in tone to my RCA 6V6GTA which I bias at 23.

I'll keep you posted.


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Post subject: Re: DRRI Bias - from Stock GT to EH
Posted: Wed Jul 06, 2011 11:33 am
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55% to 60% is ideal for me. You're correct, the data sheet does show the TAD 6V6GT STR as a 15 watt max Plate dissipation rating. So, I think that it is safe to treat it as at least a 14 watt tube. It seems that some GTs and TADs are rated at 15 watts? :?: Sounds reasonable, as I remember that the RCAs among others could routinely handle over spec wattage/voltage without so much as a hiccup.

I am running a pair of EH 6V6GT at 14 watts idle each, and they sound fantastic, with no signs of red plating at all (even with pedals), keeping a close eye on them. :idea:

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Post subject: Re: DRRI Bias - from Stock GT to EH
Posted: Wed Jul 06, 2011 12:33 pm
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Ok, I checked the bias, it was actually 19 mA at 415. So I set the bias at 23 mA and plate voltage is at 410 now. This is with the TAD 6V6GT-STR.

I did a couple of quick recordings to see if anyone notices much of a difference... I'd say there's a slight improvement overall, but there's really nothing wrong with keeping the bias at a safe level IMO, at least in my amp. I'll keep it at 23 mA for now and keep an eye on it.

Please excuse the messy playing... Strat straight into amp, amp vol at 7.

Bias at 19 mA
http://www.box.net/shared/5jc5foact047bm1f642p

Bias at 23 mA
http://www.box.net/shared/q1y3k7dalne51l7o57y8


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Post subject: Re: DRRI Bias - from Stock GT to EH
Posted: Wed Jul 06, 2011 4:24 pm
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cedarblues wrote:
Ok, I checked the bias, it was actually 19 mA at 415. So I set the bias at 23 mA and plate voltage is at 410 now. This is with the TAD 6V6GT-STR.

I did a couple of quick recordings to see if anyone notices much of a difference... I'd say there's a slight improvement overall, but there's really nothing wrong with keeping the bias at a safe level IMO, at least in my amp. I'll keep it at 23 mA for now and keep an eye on it.

Please excuse the messy playing... Strat straight into amp, amp vol at 7.

Bias at 19 mA
http://www.box.net/shared/5jc5foact047bm1f642p

Bias at 23 mA
http://www.box.net/shared/q1y3k7dalne51l7o57y8


Hard to say listening through my crappy computer speakers but I think the 23 mA sounds a little fuller, clearer, and more resonant. They both sound great in either case. :D

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Post subject: Re: DRRI Bias - from Stock GT to EH
Posted: Thu Jul 07, 2011 5:22 am
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cedarblues wrote:
Ok, I checked the bias, it was actually 19 mA at 415. So I set the bias at 23 mA and plate voltage is at 410 now. This is with the TAD 6V6GT-STR.

I did a couple of quick recordings to see if anyone notices much of a difference... I'd say there's a slight improvement overall, but there's really nothing wrong with keeping the bias at a safe level IMO, at least in my amp. I'll keep it at 23 mA for now and keep an eye on it.

Please excuse the messy playing... Strat straight into amp, amp vol at 7.

Bias at 19 mA
http://www.box.net/shared/5jc5foact047bm1f642p

Bias at 23 mA
http://www.box.net/shared/q1y3k7dalne51l7o57y8


Very tasty playing there Sir! Thanks for the sound bites. Very similar as you said.

I liked the 19ma myself. Sounded "sweeter". But just my opinion.
I'll have a go with those TADs next. May be a few weeks.

With the other tubes being stock as well as the power tubes I should probably start looking into this areas as well. But until I try the TADs I'll keep the setup the same.

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Post subject: Re: DRRI Bias - from Stock GT to EH
Posted: Thu Jul 07, 2011 1:24 pm
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bluesky636 wrote:
Hard to say listening through my crappy computer speakers but I think the 23 mA sounds a little fuller, clearer, and more resonant. They both sound great in either case. :D

Thanks! Yeah it's best to hook up your PC or laptop to a stereo system to really hear the difference... that's what I do when I want to compare something, laptop into HT system or decent headphones.

tyronne wrote:
Very tasty playing there Sir! Thanks for the sound bites. Very similar as you said.

I liked the 19ma myself. Sounded "sweeter". But just my opinion.
I'll have a go with those TADs next. May be a few weeks.

With the other tubes being stock as well as the power tubes I should probably start looking into this areas as well. But until I try the TADs I'll keep the setup the same.

Thanks! One thing at a time :) I did that for a while 'til I settled on a combination of tubes that work for me, but once in a while I'll try something new just to see if it'll work for me, good NOS tubes are not that easy to find and unfortunately cost too much.


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Post subject: Re: DRRI Bias - from Stock GT to EH
Posted: Thu Jul 07, 2011 2:47 pm
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Yes thanks for posting the clips Cedarblues, terrible playing, not, :D I am new to the DRRI, and to using a Tele. Correct me if am wrong but it seems to me it is maybe harder to get a great bridge pickup sound in comparison to the front and mixed positions. If you agree do you think bias can help get a great bridge pickup sound? Just wondering.


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Post subject: Re: DRRI Bias - from Stock GT to EH
Posted: Thu Jul 07, 2011 3:06 pm
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Magic Bus wrote:
Yes thanks for posting the clips Cedarblues, terrible playing, not, :D I am new to the DRRI, and to using a Tele. Correct me if am wrong but it seems to me it is maybe harder to get a great bridge pickup sound in comparison to the front and mixed positions. If you agree do you think bias can help get a great bridge pickup sound? Just wondering.

You're welcome! :) proper bias can help with everything IMO. I can get some sweet tones out of the bridge pickup, but my amp is not your average DRRI... what's bothering you about the bridge tone? Too bright? I like to keep the treble up on my amp, so if I find a pickup is too bright sounding I use the tone on the guitar, I don't like to turn the treble down too much on the amp, I feel like I loose a lot of the character of the amp. That's why I make sure my Strats have tone control on the bridge. Albert Collins who plays a Tele :) used to set his vol at 10 treble at 10 and bass at 0! He wasn't playing through a DRRI, I know, but I'm giving you an example of the tone you can get with a Tele and a Fender tube amp :)

Where do you usually set the volume on the amp? IMO it sounds kinda thin at lower volumes, specially with the bridge pickup.


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Post subject: Re: DRRI Bias - from Stock GT to EH
Posted: Thu Jul 07, 2011 3:29 pm
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Albert's hallmark amp was a Quad Reverb loaded with JBL D120F's. And he played with the middle control maxxed out as well. I doubt that any note played through that amp would mimic what a DRRI produces.

JMO

Arjay

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